diff --git a/rfc2047.c b/rfc2047.c
index b9c41ab..b3782fb 100644
--- a/rfc2047.c
+++ b/rfc2047.c
@@ -24,7 +24,7 @@ blaze822_decode_qp(char *start, char *stop, char **deco, size_t *decleno)
 		-1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1
 	};
 
-	char *buf = malloc(4 * (stop - start) + 1);
+	char *buf = malloc(stop - start + 1);
 	if (!buf)
 		return 0;